Using stable isotope natural abundances (delta N-15 and delta C-13) to integrate the stress responses of wild barley (Hordeum spontaneum C. Koch.) genotypes

To integrate the complex physiological responses of plants to stress, natural abundances (delta) of the stable isotope pairs N-15/N-14 and C-13/C-12 were measured in 30 genotypes of wild barley (Hordeum spontaneum C, Koch,), These accessions, originating from ecologically diverse sites, were grown in a controlled environment and subjected to mild, short-term drought or N-starvation, Increases in total dry weight were paralleled by less negative delta(13)C in shoots and, in unstressed and droughted plants, by less negative whole-plant delta(13)C. Root delta(15)N was correlated negatively with total dry weight, whereas shoot and whole-plant delta(15)N were not correlated with dry weight. The difference in delta(15)N between shoot and root varied with stress in all genotypes, Shoot-root delta(15)N may be a more sensitive indicator of stress response than shoot, root or whole-plant delta(15)N alone. Among the potentially most productive genotypes, the most stress-tolerant had the most negative whole-plant delta(15)N, whether the stress was drought or N-starvation. In common, controlled experiments, genotypic differences in whole-plant delta(15)N may reflect the extent to which N can be retained within plants when stressed.